This post is misleading and outright false in some respects. From the first article posted:

"By Claire Kirch | May 31, 2020

The civil unrest in the Twin Cities continues to take its toll on Minnesota's literary community—sometimes in unexpected ways. Thursday evening, the night before protesters set fire to two adjoining Minneapolis indie bookstores and destroying them both, the reaction to a St. Paul–based literary agent’s tweet ended up gutting the boutique agency she owns.

Three agents affiliated with Red Sofa Literary tweeted this past weekend that they have resigned in response to owner Dawn Frederick’s tweet, leaving one subsidiary rights executive besides Frederick still employed there. Frederick's official Red Sofa account on Twitter has been removed."

"Frederick, who founded Red Sofa in 2008, is a well-known fixture in Minnesota’s vibrant literary community, serving on the board of directors of the Loft Literary Center and having launched the MN Publishing Tweet Up social group. She also supervises the team of volunteers working in the galley room during the Heartland Fall Forum regional booksellers trade show each year."

So no, this was not during the BLM protests in St. Louis as the date of the article precedes when those began. Furthermore she is a "well-known fixture in Minnesota's vibrant literary community", and has been since 2008, which is something I would have expected someone who "worked in publishing for years" to be aware of.

Throwing her name combined with BLM into search engines like google only returns results after this event, so your assertion of her advocacy is unfounded and not to be believed by the above and what follows.

"Minneapolis attorney Marshall Tanick of the Meyer, Njus, Tanick law firm emailed cease-and-desist letters on Monday to two literary agents and an author on behalf of his client, Dawn Frederick of Red Sofa Literary. The two agents are Beth Phelan of Gallt and Zacker (the email was cc’ed to that agency’s two principals) and Kelly Van Sant, who until two weeks ago worked for Red Sofa. The author is Isabel Sterling, who writes YA novels. SFF author Foz Meadows also received an email, she tweeted, but it contained multiple factual errors and was recalled by its sender."

"UPDATE: On Thursday afternoon, Laura Zats, a principal of Headwater Literary Management in Minneapolis announced that she received a letter from Frederick's lawyer, threatening legal action against the agent for re-tweeting tweets by others alleging that Frederick is racist. Zats is a former employee of Red Sofa Literary, who left it last year ago to found her own agency. She has joined Phelan, Van Sant, and Sterling in their GoFundMe campaign soliciting funds in case of a lawsuit. The campaign has raised almost $15,000 to date.

Several authors have announced that they are severing their relationships with Red Sofa Literary, including Margot Atwell, the head of publishing for Kickstarter. She tweeted Thursday afternoon that she has terminated her relationship with Frederick "due to the choice she made to call the police during the protests against George Floyd’s murder in Minneapolis, and her subsequent decision to threaten legal action against her critics."

https://www.publishersweekly.com/pw/by-topic/industry-news/p...

So Frederick decides to start suing people, which results in agents/authors not targeted in lawsuits to cut ties with her in part due to her legal efforts.

Had she stuck with the apology she released a few days after the tweet, instead of doubling down and even throwing lawsuits around, things would have likely been far better for her. Or even not publicly announcing she was calling the police during protests against police behavior.

In other words she's not the blameless martyr you make her out to be.

And finally cancelling is just a propaganda term on the political right to escape the negative consequences of their actions. This is evidenced by it not being applied when, say the (Dixie) Chicks criticized President Bush and had their careers largely ended. It's also not applied when the 'cancelling' is apolitical, such as a restaurateur who alienates their customers/community (think Cafe Hon from Kitchen Nightmares).

EDIT: Less than 2 minutes after this was posted it was down voted and flagged.